The general concept of a parallel ruler, i.e., an instrument which is reliably adjustable to enable the formation of a series of parallel lines, is well-known in the art. Examples of U.S. patents which show parallel rulers, also referred to as parallel liners, section liners or section rulers, or related instruments include U.S. Pat. No. 455,779 (Terry), U.S. Pat. No. 598,875 (King), U.S. Pat. No. 600,758 (Warren et al.), U.S. Pat. No. 648,396 (Eaton), U.S. Pat. No. 669,239 (Hill), U.S. Pat. No. 826,471 (Riedel), U.S. Pat. No. 1,066,576 (Benton), U.S. Pat. No. 1,092,107 (Jacobsen), U.S. Pat. No. 1,117,092 (Riedel), U.S. Pat. No. 1,349,550 (Magnuson), U.S. Pat. No. 1,422,641 (Walters), U.S. Pat. No. 1,464,973 (Dargue et al.), U.S. Pat. No. 1,469,192 (Shepard), U.S. Pat. No. 1,600,545 (Hooper), U.S. Pat. No. 2,089,757 (Nieukamp), U.S. Pat. No. 2,239,323 (Hicks), U.S. Pat. No. 2,420,090 (Nelson), U.S. Pat. No. 2,879,597 (Burger), U.S. Pat. No. 4,364,184 (Dowzall), U.S. Pat. No. 4,539,759 (Dowzall et al.) and U.S. Pat. No. 4,790,077 (Tsujioka).
All of the references mentioned above are incorporated by reference herein.